The present invention relates to an inlet for a fluid tank such as a vehicle fuel tank. In particular, the present invention relates to an anti-siphon inlet for a vehicle fuel tank.
The theft of fuel by siphoning from the fuel tanks of vehicles, and in particular commercial road vehicles, is a recognized problem. It is known to fit vehicles with a lockable fuel tank filler cap to prevent unauthorized access to the tank inlet. However, since the fuel filler cap is accessible it is vulnerable to tampering and can often be forced open by the determined thief. In addition, it is not always practical to fit a vehicle with a lockable fuel filler cap.
This problem has been addressed in the prior art by provision of a fluid tank inlet incorporating structure to prevent insertion of a siphon tube into the tank. For example, WO2006/048659 discloses an anti-siphon fluid tank inlet assembly comprising a tubular inlet body which in use is secured to the normal tank inlet so that its distal end extends a short distance in to the tank. The tubular inlet is designed to receive a conventional fuel dispensing nozzle. A conically shaped baffle is provided at the distal end of the tubular inlet to prevent insertion of a siphon tube through the tubular inlet and into the tank below. Both the tubular wall and the conical baffle are provided with apertures sized to allow the egress of fuel but block insertion of a siphon tube of any practical diameter. The inlet is designed so that fuel hitting the conical baffle either passes through the apertures in the baffle or is deflected towards apertures in the tubular body.
With such anti-siphon inlets, fuel can only be siphoned to the extent that the fuel level is above the base of the conical baffle. It is therefore desirable for the tubular body to be as short as possible. However, the shorter the tubular body the more prone the inlet becomes to the problem of “backflow”. That is, if fuel does not flow through the inlet at a minimum rate, fuel can well up within the inlet and either spit out of the inlet or cause sufficient back-pressure to activate the filler nozzle automatic shut-off mechanism thereby interrupting fuel delivery.
Hence, there exists a need in the art for systems and methods to mitigate the aforementioned limitations.